1. Field of the Invention
The present invention relates to a numerical control device, and particularly to the numerical control device for calculating optimum acceleration in reverse operation.
2. Description of the Related Art
In velocity control of a feed shaft of a machining tool, instant output of velocity signal commanded by the program generates rapid acceleration and rapid time derivative of acceleration (hereinafter referred to as “jerk”) to cause a large amount of impact and machining error for the machining tool. Japanese Patent Laid-Open No. 59-062909 discloses a technique in which acceleration and jerk is suppressed by filtering acceleration/deceleration, to avoid a great impact on the machining tool. The technique for control, described above, effectively suppress the impact on the machining tool when change of moving direction of the feed shaft generates a corner in a machining path.
The technique descried in Japanese Patent Laid-Open No. 59-062909 causes difference between the machining path commanded by the program and the machining path generated by the filtering process. The filtering of acceleration/deceleration, when change of movement direction of the feed shaft generates a reversal in the machining path as described above, brings a problem that the path does not reach a commanded reversing point. To solve the problem, the feed shaft stops and the acceleration is controlled to be 0 at the reversing point so that the path error caused by the filtering process is suppressed and deviation of arrival position is avoided.
However, there is a problem that, re-acceleration time, needed when the acceleration is set to be 0 by filtering the acceleration/deceleration, increases the cycle time.